Bicycle gear shift repair

ABSTRACT

A bicycle gear shifting device including a ratchet plate, a pawl, and a spring biasing the pawl for engaging teeth on the plate, no longer functions properly because the spring is unable to exert an adequate bias force; this condition is repaired by connecting a supplemental spring to the device for biasing the pawl into engagement with the ratchet teeth, without replacing the original spring.

United States Patent Sullivan, Jr. July 3, 1973 54] BICYCLE GEAR SHIFTREPAIR 3,154,176 10/1964. Smith 29/401 x Inventor: Daniel AndrewSullivan, Jr, c/ 3,481,2l7 12/1969 Maeda 74/489 Alcoa DevelopmentCommunity, R.D. No. 2, Rt. 780, New Primary ExaminerCharles W. LanhamKensington, p 150 Assistant Examiner-D. C. Reiley, ll]

[22] Filed: Apr. 26, 1972 21 Appl. No.: 247,660 [57] ABSTRACT A bicyclegear shifting device including a ratchet plate, 1521 vs. c1. 29 40174/489 Paw, and a p g i sing thepawl for engaging 16am [5 1] Int. L u 57/00 on the plate, no longer functions properly because the 1581 Fieldof Selach: ....:.::-.I: 29/401- 74/5711 488 Spring is unable an adequatebias fme; this r a condition is repaired by connecting a supplementalspring to the device for biasing the pawl into engage- [56] ReferencesCited ment with the ratchet teeth, without replacing the origi- UNITEDSTATES PATENTS 2,770,980 11/1950 Millward 1., 74/489 3 Claims, 2 DrawingFigures 1 BICYCLE GEAR SHIFT REPAIR BACKGROUND OF THE INVENTION Thepresent invention relates to bicycle gear shifting devices usuallymounted on bicycle handle bars and including a ratchet plate, a pawl,and a spring for biasing the pawl into engagement with ones of theteeth.

Such gear shifting devices are generally sold rivetted together, so thatit is impossible to replace the spring. once it has failed to exert itsbiasing function adequately. Spring failure can arise due to, forexample, fatigue, creep, yielding, and corrosion. When a spring hasfailed in such devices, it has been the prior practice to remove thedevice with the faulty spring from the bicycle handle bar and replacethe old device with a new one.

SUMMARY OF THE INVENTION An object of the present invention, therefore,isto provide a simple method of repairing a gear shifting device of theabove described type having a faulty spring,- which method includes theadvantages that no effort is expended to remove the faulty spring andthe device need not even be removed from a handle bar on which it ismounted.

This, as well as other objects which will become apparent-in thediscussion that follows, are achieved according to the present inventionby connecting a supplemental spring to the above described device forbiasing the pawl into engagement with the ratchet teeth, withoutreplacing the original spring.

BRIEF'DESCRIPTION OF THE DRAWING plane 2.-2. of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, agear shifting device of the type intended for the method of theinvention is shown attached to a handle bar 25 of a bicycle by a clamp24.

The housing of the gear shifting device includes perimetral wall 13 andtwo opposing plates, one of which is exposed in FIG. 1, the other beingplate 26 appearing in FlG. 2. Plate 26 does not appear in FIG. 1, ithaving been removed for the purpose of exposing the internal structureof the gear shifting device. Plate 26 is usually permanently secured inplace to permanently close the housing, either by rivetting to theopposing plate or by welding to the perimetral wall 13. Perimetral wall13 extends only through about l80 of arc, in order that lever 21 be freeto perform its functions.

Ratchet plate 19 is pivotally mounted about pin 20, which is securedbetween the two opposing plates. Plate 19 may be rotated about pin 20 bymanual pulling on lever 21 in the direction of arrow A. Lever 21 ispivotally connected to plate 19 at pin 23 and its pivoting in thedirection of arrow A is stopped by lug 22 securred on the surface ofplate 19. Thus, when lever 21 comes in contact with lug 22 when beingpulled in the direction of arrow A, then plate 19 rotates about pin 20,with lever 21.

Plate 19 is generally biased for rotation in the direction of arrow Bbythe force F exerted by flexible cable 11, which is secured as shown tothe plate. Flexible cable 11 extends through tube 10 to the rear axle(not shown) of the bicycle.

A rigid turret l2 is secured to the perimetral wall 13 at the holethrough which cable 11 passes. I

Pawl 15 is mounted"'pivotably to pin 16 and engages with one of ratchetteeth 18a, 18b, and 181: for locking plate 19 into various positions.Moving of plate 19 for engaging one of teeth 18a to 18c with pawl 15pulls cable 11 correspondingly, thereby selecting the position of cable11 and thus the particular gear that the bi cycle is in. Pawl 15, in anew and properly functioning gear shifting device, is biased intoengagement with the teeth by spring 17. The left side of spring 17 inFIG. 1 is welded to wall 13. The pawl can be released from the teeth bymoving lever 21 in the direction of arrow B, so that the lever comesinto engagement with the pawl and forces the pawl free of the particulartooth engaged at the time.

During use, the part of the gear shifting device that usually fails isspring 17, it no longer performing the function of biasing the pawl intosecure engagement with the ratchet teeth of plate 19. With the housingpermanently closed, it is not possible to replace the spring and it thushas been necessary to go to the expense of replacing the entire gearshifting device.

Spring failure can occur in a number of ways. Metal creep or corrosioncan, for instance, lead to a reduction of the spring constant k f/x,where f equals force and 2: equals displacement. Thus, while spring 17is shown still bearing against pawl 15 in FIG. 1, the bias force maynevertheless no longer be sufficient to keep the pawl engaged with tooth18a, due, for instance, to the presence of force F and/or to forcesarising from bumps in the street pavement. There can also be a permanentplastic deformation of the spring, so that the spring is no longer ableto remain in contact with pawl 15 when the pawl is in the position shownin FIG. 1. In FIG. 1, there may be, for instance, a gap, about equal tothe thickness of the spring wire, between the spring and the pawl in theposition shown; the gap may even be so large that no pawl-spring contactis present even when the pawl has rotated in the direction of arrow Bsuch that its tip has passed-by the tipof tooth 18a.

According to the method of the present invention, a gear shifting deviceof the above-described type is repaired by connecting a supplementalspring 14 to the device forbiasing pawl 15 into engagement with theratchet teeth, without replacing spring 17 and even without removing thegear shifting device from the bicycle.

In the preferred embodiment shown, supplemental spring 14 is a piece ofhay baling wire of around 0.05

inches diameter bent approximately into the configuration shown. Thebending tends to cold work the wire and to increaseits yield strength,thus increasing its effectiveness as a spring. The supplemental springhas a generally U-shape in FIG. 2, with the inside of the base of the Ulying in contact with turret 12. As shown, the supplemental spring alsohas a U-shape in FIG. 1, with the base of the U-shape there being thehigh point in the Figure, one leg being connected to turret 12, theother leg bearing against pawl 15. The bias force arises from thetendency of the leg bearing against the pawl to coil around toward theleg connected to turret 12.

it will be realized by those skilled in the art that l have chosen mypreferred embodiment because I could easily reduce it to practice and besure that it works. Naturally, the means for carrying out the method ofthe invention is capable of being presented in a more polished, salableembodiment by modern production methods.

I claim:

1. A method of repairing a gear shifting device comprising in assembly aratchet means for pulling a flexible linkage into a plurality ofselected positions, pawl means for engaging with ratchet teeth on saidratchet means for locking said ratchet means in any one of said selectedpositions, and spring means for biasing said pawl means into engagementwith said ratchet teeth, which spring means no longer performs itsfunction of ing, said housing having a rigid turret securred theretothrough which said flexible linkage extends, the connecting of thesupplemental spring being betweensaid turret and said pawl.

3. A method as claimed in claim 1, said gear shifting device furtherincluding a permanently closed housing about said spring means.

1. A method of repairing a gear shifting device comprising in assembly aratchet means for pulling a flexible linkage into a plurality ofselected positions, pawl means for engaging with ratchet teeth on saidratchet means for locking said ratchet means in any one of said selectedpositions, and spring means for biasing said pawl means into engagementwith said ratchet teeth, which spring means no longer performs itsfunction of biasing said pawl means into engagement with said ratchetteeth, which method comprises connecting a supplemental spring to saiddevice for biasing said pawl means into engagement with said ratchetteeth, without replacing said spring means in said device.
 2. A methodas claimed in claim 1, said ratchet means and said pawl means includinga common housing, said housing having a rigid turret securred theretothrough which said flexible linkage extends, the connecting of thesupplemental spring being between said turret and said pawl.
 3. A methodas claimed in claim 1, said gear shifting device further including apermanently closed housing about said spring means.